Smartphone good applications to have on the phone before I go. England

Navigation on foot and using public transportation. This is a big one. Will use it to call as needed. May have uses I have not thought of. Also thank you for the information will look at it.

Tube Map London

Google Maps - already on Android phones.

Google Hangouts - free voice calls to US phone numbers, even to landlines (disregard if you aren't from the US). Nice to be able to call your airline or bank in case of a problem, without needing to worry about how long on hold, etc. Will work even on WiFi if you have no mobile service at all.

(Hangouts is being replaced later this year with Google Voice VOIP. You can try it already, but you need to sign up for Google Voice which is slightly more involved than just firing up Hangouts)

Any bus and train apps for the towns you will be visiting (e.g. if you will be in London, find the official app for tube and bus schedules, etc. though Google Maps should already help you with routing).

I really like Maps.me for navigation. Download the maps when you have wifi and then you can get walking directions, etc., similar to GPS offline.

Here's the best app to have but only if you get those you want to stay in contact with to also upload to their phones. WhatsApp. Believe it's still free.

I learned of it 3 years ago when my London AirBnB host was heading to China and wanted us to stay in contact. Her job takes her all over Europe and Asia and she uses it everywhere.

You can engage in video calls, send text and pictures freely. It's how I stay in contact with friends in England when I'm back in the states and vice versa. Used it yesterday to video chat with a friend working on TV show being filming in the UK and another friend in San Francisco to discuss the tickets for our annual SF GIANTS vs LA Dodgers baseball game.

I travel to London nearly every year and like CityMapper. Haven't yet uploaded the Tfl App. I simply use google and the tfl.gov.uk link is there from memory. Excellent for planning a outings when not on the tour.

As its your first trip you might consider the Currency Converter app till you get the hang of doing the math from pounds to dollars in your head.

Enjoy the tour!

The app for your airline. You can check in online, be notified of any changes or problems, etc.

Not an app, but something that was very helpful to me: Many attractions now have a discount for online booking (anywhere from £1 to £5.25). However, registering your data on a phone is quite difficult. So, if there are any places you're thinking of going on your free time, look now at the websites to see if they have an advance booking discount. If they do, register and create an account on your home computer (much easier than on the phone). Then, if you do want to go, you can just log in on your phone and buy the discounted ticket. I used this trick for Greenwich sights with great success.

Smart tip from Harold. I did this for my trip to Oslo last with the apps for public transit and the train from the airport. I could bypass the machines and just bought my ticket on my phone since I had already registered my card details!

Anyway for London: CityMapper app (free), which is indispensable (but requires use of data while you're there). Will give you the various options for routes for the place you're getting ready to go (how long will it take by bus, and where and when to get off? Or by Tube, and give you the various options, including where to position yourself on the platform to be best positioned to transfer to your next train or be closest to the exit you'll need. . .or how long it will take by walking or biking, or by taxi and estimated cost . . ..). It's continuously updated with live information from the London transit authority, so it can advise you of delays or shutdowns too. It has taken the guesswork out of getting around!

Depending on how much scope you have for free time or if you're arriving or departing after the tour with extra days to spare then the English Heritage and National Trust apps are good for indicating their nearest sites to your location.

If you will travelling anywhere by train (not Tube) I advise to load the app for each train company you will use and National Rail. It is handy to get real time running info, as well as platform changes, alternate routings in case of disruption and calling patterns.

A weather app - the BBC does a good one.

If you use Twitter follow Elizabeth Rizzini. She is a Met office / BBC weather expert and often tweets a personal forecast for the London area with a degree of British humour. @lizzieweather

A white noise app to help sleep if there is a bit of street noise - I like two, iFirePlace for a roaring fire or a slow fire, and my favourite SM: Rain which gives a nice rainfall of various intensities

your banking apps so you can keep control while away - but you probably already have those

Wunderlist for all sorts of lists

Blue Plaques - does what it says on the tin, including guided walks, useful for understanding one you are nearby or just passed on the bus or finding one - a personal treasure hunt - maintained by English Heritage who are responsible for the blue plaques

CityToiletFinder - helps you find a - you know - in the City of London

another vote for CityMapper

... but mostly, put the phone away and enjoy the city.

oh, and don't put your phone down on a table unattended, even sitting next to it or it may go poof

So many good answers. Things I have thought of and with improved ways of doing. Also good things I did not even think of as uses. Thanks to all

I use Google maps and I download maps of each city I'm visiting before I go (they expire within 30 days so make sure you download or update your offline maps in the week before you go). It has been very helpful getting around on foot while in Europe.

Oyster Card app. You can register your Oyster Card and it will tell you how much money you have left on your card and a warning when you get low. It also has a link to the tfl journey planner. And if you lose it you can report it.

You will have to give a local address. I just used my hotel. No problem. If you are only in London a couple of days, you probably don't need this.

I will suggest the following, some of which have already been mentioned:

Citymapper
Your airline
Currency Converter
Mobile Passport (if you don't have Global Entry)
Tube Map
London Bus map
Weather app
Rick Steves Audio Europe
Skype (similar to Google Voice)

I can't believe I forgot Mobile Passport! If you don't have Global Entry, and will be entering the US at one of the 25 included airports, this is a MUST. It will save you lots of time and hassle. Set up each traveler in your party in the app before you leave the US. It can be a bit tricky to find the Mobile Passport lines at the entry airport, and you do need to have both the app and your passport for both the immigration step and the customs step. You are then set to breeze through the process.

Details here: https://www.cbp.gov/travel/us-citizens/mobile-passport-control

CAMRA app (https://gbgapp.camra.org.uk/)

I take notes on my phone while I'm out and about - to remember what I saw/did plus notes about photos (it is easy to forget why you took a picture of what looks like nothing but is actually the cornerstone to some amazing building). I don't like the basic notes app on my phone, so I downloaded a free app that is more flexible for my uses. I also do a travel blog, so I make sure the Wordpress app is downloaded and working. I make sure there is a currency conversion app that doesn't need cell data (because I'm terrible at math in my head). I store back up files (scans of passport, hotel contact info, emergency numbers for credit cards) in Dropbox and open them on the phone before leaving the US (so they're cached on the phone and don't need a cell or wifi connection to open).

@CL — I hate the stupid “Notes” app I have on my phone — do you mind sharing which one you use?

Yes. Excellent recommendation regarding Mobile Passport.

Hello!I'm a new one and interested in some offline maps and some translator, did someone know good ones?

The translator app I use on my iPhone is Google Translate. You can type in the word or phrase, speak it, write it with your finger or snap a pic with your camera to translate. It has lots of languages. I have used Dutch, French and Spanish. The most recently used language appears at the top of the list so you don't have to search for it every time you need it. Put it on your phone and play around with it before you go. It is very easy.

I think these are the most important one's
Tube Map
London Bus map
Weather app